The problem can be stated very simply. The rear derailleur undershifts in the middle of the cassette and overshifts on the 2 or 3 biggest cogs. Hanger is straight, cables and housing replaced, cassette lock ring properly torqued. The wheels are Campagnolo Shamal Ultra. Nothing seems to make any difference.
Since my last post the bike has been with a very experienced Campy mechanic who has run out of ideas. (I really don't think there is any problem with compatability between the frame/hanger and the rear derailleur). He was in touch with Campy and they are sending him a "special part" that they believe may fix the problem. This bit sounded a bit fishy to me.
Tomorrow I will call. If they don't have a fix I think we are at the point where they should simply replace the shifter and the rear derailleur.
Graeme, in your experience have you had luck with longer cage derailleurs solving mysterious shifting issues? I know there is a mid-cage Record rd and I wonder if that might just do the trick. I have found that on every bike where I have changed from short to mid cage derailleurs, the shifting has improved. My experience has been with Sram and Shimano thus far, but perhaps my Record groupset will benefit as well. My cassettes are 11-28 (11-29 for Campy) and I suspect the big spread may be part of the issue.
And not that it may matter for service, but I am not in the US. Rather I'm in Canada, so yeah we have the Queen also.
